Implementation plan/timetable: Enrollment of subjects by Dr. Mala Sachdeva, and Peter Durkin, PA will begin once the protocol has been approved by the IRB. The sites of patient identification and enrollment, and baseline specimens will be the Renal Clinics at Montefiore and Weiler Hospitals, and from the Renal Faculty practices. Follow-up specimens will be drawn at the above sites, while the patients are pre-hemodialysis, and will be drawn before the dialysis session for patients already receiving hemodialysis. Both preliminary and follow-up data entry will be performed by Dr. Mala Sachdeva using SPSS. Patient charts/records and specimens will be coded to ensure confidentiality. Specimens and charts will be stored as described above. Data analysis will be performed by Dr. Mokrzycki, Dr. Sachdeva and Dr Kathrine Freeman. The anticipated duration of the study is 3 years: approximately 2 years for patient enrollment and 1 year of follow-up data and time for data analysis.